Electrical sound blooping



Aug. 4,` 1942.

B. KREUZER ELECTRICAL SOUND BLOOPING Filed June '7. 1940 2 Sheets-Sheetl @www Patented Aug. 4, 1942 Y l ELECTRICAL SOUND BLGOPING BartonKreuzer, Los Angeles, Calif., assignor to Radio Corporation of America,a corporation of Delaware Application June 7, 1940, Serial No. 339,296

10 Claims.

This invention relates to sound motion picture apparatus andparticularly to sound rerecordlng systems.

In the production of a sound motion picture it is well known that thefinished picture is made up of a large number of separate sequencestaken at different times during the production period of the picture.The concomitant sound sequences are generally taken simultaneously withthe respective picture sequences. During the course of production,various numbers of sequences are spliced together for review, editingand rerecording purposes. In this procedure, the picture film and soundfilms are simultaneously projected and reproduced, respectively, andthis is usual- 1y accomplished in individual picture and soundapparatus.

The first sound record, therefore, contains manysplices which, whenpassing between the light source and photoelectricr cell in the soundhead, produce plops or clicks. To prevent these extraneous noises,several methods have been employed in the past, such as the manualpainting out of the splices by black paint applied to the splice pointor over the images of the splices, or by a mechanical shutterarrangement in the sound head itself. This procedure of eliminating theeffect of a splice ls known as blooping," one form of the shutter typeof blooper being illustrated in U. S. Patent 1,810,- 527, of January 16,1931.

The present invention is directed to a specific form of blooping systemwherein the effect of a splice or any other extraneous densityvariations in the sound track portion of the film is prevented frominterfering with the sound track reproduction. In the usual type ofshutter blooper the light beam of constant intensity is graduallyeliminated from the sound track at the splice, and consequently from thephotoelectric cell, and then gradually returned to the film, the desiredperiodicity of the increase and decrease in light being belowaudibility. In other words, the elements varying the light beam must beso timed as not to introduce noise by their own operation.

The present invention is directed to a method of and system for varyingthe transmission in the reproducing circuit intermediate the sound headand a sound rerecorder loudspeaker or monitor, the rate at which thetransmission is decreased and increased being determined by electricaltiming circuits. In this manner the timing is easily controllable withaccuracy, the

operating characteristic than is found in the use of mechanical deviceswhich must be built into the sound head itself.

With the present invention the only element located at the sound head isa circuit contacter operable by either holes in the film, notches in thefilm, metallic elements adhering to the film, or by the increase inthickness of the film caused by the film splices themselves. When anelectrical contact is produced by one of these modifications to the filmpassing a predetermined point, a relay may be actuated which will modifythe transmission characteristic of the reproducing transmission circuitto reduce transmission or increase attenuation at a certainpredetermined rate and to restore the circuit at another rate, theserates being such as not to introduce an audible variation at theloudspeaker or upon the film when the rerecorded sound track isreproduced.

The principalobject of the invention, therefore, is to facilitate thereproduction of spliced sound record film or film having variations inlight densities thereon which cause extraneous reproduced noises.

Another object of the invention is to electrically reduce and restorethe transmission of a reproducing sound circuit at an inaudible rate.

A further object of the invention is to bloop a sound record film byvarying its transmission circuit.

A further object of the invention is to provide a timing circuit for anelectrical transmission circuit which introduces an inaudible varia-`tion in the reproduced sound.

A further object of the invention is to control the shunt impedance of atransmission circuit at a predetermined rate under control oi areproduced film being transmitted by the circuit.

Although the novel features which are believed to be characteristic ofthis invention are pointed out with particularity in the appendedclaims, the manner of its organization and the mode of its operationwill be better understood by referring to the following description readin conjunction with the accompanying drawings forming a part thereof inwhich Fig. 1 is a combination schematic and diagrammatic drawingembodying one modification of the invention;

Fig. 2 is a detail of a variation of the modification shown in Fig. 1;

Fig. 3 is a schematic drawing of another modientire system lendingitself to a better overall iication ofthe invention; and

Figs. 4 and 5 are detail views showing variations of the modificationshown in Fig. 3.

Referring now to Fig. l, a soundhead 5 having a film magazine 6translates the variations in transmission through the sound track areaof a iilm into electrical currents which are transmitted over conductors1 to a transformer 8. Transformer 8 feeds an amplifier tube 9 which iscoupled by resistances I8 and II and a condenser I3 to a standardamplifier I5, the amplifier I5 feeding a sound recorder I6 with its filmmagazine I1 when switch 28 is closed. For monitoring and rehearsalpurposes a loudspeaker I8 is provided. In the sound head 5 is showndiagrammatically a Contact switch 22 which may be of any standard typeoperable by film notches or any other modifications to the film beingreproduced as mentioned above. The contacts 22 are connected overconductors 23 through a potential source 24 to a relay 25. Energizationof the relay 25 will close a contact 26, thus closing a circuit througha potential source, such as a battery 21, a resistance 28, apotentiometer resistance 29 shunted by a potential source, such as abattery 30, and the cathode and grid of tube 33, these elements justrecited being connected in series. Shunted across the contact 26,battery 21 and resistance 28 is a condenser 34 and a resistance 35.

The tube 33 has its anode to cathode impedance shunted across thetransmission circuit connecting tube 9 with amplier I5. By the initialadiustment of the potentiometer resistance 29, the impedance of ytube 33is made high so that this tube normally has a negligible effect upon thetransmission circuit. It will be observed that the cathode is connectedto ground at 31, while the positive terminal of potentiometer resistance29 is also connected to ground. Thus the transmission of the electricalcurrents from the sound head 5 over the transmission circuit will benormal with the contact 26 open. When the contact 26 is closed, however,by the energization of relay 25, the grid of tube 33 is given a positivepotential from the battery 21 which will reduce the anode-cathodeimpedance of the tube and thus lower or attenuate transmission over thereproducing circuit. The amount of this reduction is, of course,controlled by the value of the potential source 21, resistance 28, thesetting of potentiometer resistance 29, and the ratio of resistance 35to resistances 35 and 28.

The rate of attenuation is primarily determined by the values of theresistance 28 and resistance 35, while the rate at which the system willbe restored to its .normal operating characteristic after the contact 28is opened is primariiy determined by the rate of discharge of condenser34 through resistance 35. This timing circuit just described is easilyadjusted and predetermined so that the decrease in the transmissioncharacteristic and increase therein may be at a rate sufficiently low asnot to be audible at the speaker I3. Furthermore, there will be notransmission to the sound track modulating elements in the recorder I8while contact 28 is closed.

the contact 26 is open, which is the normal position, the tube 39 willhave a high impedance due tential as the cathode, and the impedance ismaterially decreased. This circuit, of course, will provide a more rapidaction than the timing circuit of Fig. 1.

Referring now to Fig. 3, a standard type of rerecording amplifiercircuit'is disclosed in which the input to a transformer 43 is connectedto the sound head, while the output of the transformer is impressed upona screen grid tube 44. The output of tube 44 is coupled to an amplifiertube 45 by resistances 46 and 41, a condenser 48 and a timing circuitcomposed of a resistance 49 and a condenser 50. The output of tube 45 istransmitted through a transformer 52 to another amplier, such as isshown at I5 in Fig. 1. The potential supply for the screen grid tube 44is obtained from a B-supply connected at 54 to a potentiometercomprising resistances 55, 56 and 59 and a series resistance 51. Theanode potential for tube 44 is obtained over resistance 51, a contact 58and resistance 46, while the screen grid potential of tube 44 isobtained over resistance 51, contact 58 and a resistance 60. The B-minuspotential is connected to the potentiometer at 62;l one lead to thephotoelectric cell is connected at 63; the cathode is connected at 1 6|,while conductors 64 from relay 65 go to a Referring now to Fig. 2, itwill be observed film-controlled contactingdevice such ras shown at 22in Fig. 1.

In the operation of the above circuit, the transmission tube 44 itselfis operated upon to reduce or attenuate transmission therethrough at apredetermined rate.4 The normal condition of contact 58 is closed, asshown, so that the anode and screen grid of tube'44 is energized fromthe B-supply. However, upon actuation of the relay 65 which openscontact 58, the anode and screen grid potential is removed from the tube44 at a rate principally determined by the discharge of condenser 66shunted across the anode-cathode and screen grid-cathode circuit.By-pass condenser 61 and certain other circuit elements also have aslight effect on the rate of attenuation. The restoration rate for thetube 44 when the contact 58 is closed is determined by the value of theresistances 51, 46 and 60 and condensers 66 and 61. Thus, by varying thevalues of re sistances 51, 46 and 60 and the value of condenser 66, adefinite rate of decrease and increase in the transmission rates isobtainable which will provide an inaudible signal either at the monitorspeaker I8 or at the recorder. 1

A variation of the timing circuit shown in Fig. 3 is shown in Fig. 4,wherein the anode and screen grid of tube 44 is connected at point 68 onthe potentiometer 55, 56 and 59,*the cathode, to the point 69, while thepositive B potential terminal is connected through resistance 51 and a.contact 1I. A condenser 12 is bridged across potentiometer resistances55, 56 and 58. In this variation, breaking of the contact at 1I' removesthe B potential from the anode and screen grid of tube 44, and the rateof decrease in transmission of the tube is dependent upon the rate ofdischarge ofcondenser 12 through resistances 55, 56 and l59 and othercircuit elements. The restoration period, of course, is determinedprimarily by the value of resistance 51 and resistances 46 and 60, as inFig. 3.

In Fig. 5, only the potential on the screen grid of tube 44 is varied bythe relay 65. In this embodiment, the potential t the screen grid issupplied over a resistance 14 through contact 15 to the B potentialsupply shunted by a condenser 16. The contact 15 is normally closedwhile the contact 11 is normally open. Upon actuation of the relay 65,however, contact 15 is broken and contact 11 is made, which removes theB supply from the screen grid and lets it decay at a rate determined bythe rate of discharge of condenser 16 through resistance 14. Uponde-energization of relay 65, however, restoration of transmission to thecircuit is controlled by the value of resistance 14. The values of othercircuitrelements, of course, modify the values of the resistance 14 andcondenser 16.

In the above modifications, electrical control of transmissionattenuation is produced by a variable shunt in the transmission circuitand by varying the attenuation of one of the transmission elementsitself. In each case, the variations in the rate of transmission decayand restoration is easily controllable so that any desiredcharacteristic may be obtained. Furthermore, this type of control may beintroduced in the circuit away from the sound head except for the smallcontacting device which may be positioned at any easily accessible pointeither in the sound head or in the film magazine, which arrangement doesnot interfere with the optical elements in the sound head itself. In amechanical shutter system, if the edge of the shutter does not interceptthe light beam properly to produce inaudibility of the bloopingoperation, it is difficult to alter the condition.' With the presentelectrical blooping circuit any resistance or condenser may be madevariable for this purpose. Furthermore, the circuit maybe manuallycontrolled if such operation is desired.

I claim as my invention: I

1. A sound transmission system for a sound record having extraneousmodulations therein comprising means for translating said record intoelectrical currents corresponding thereto, means for transmitting saidcurrents, means for attenuating the transmission of said currents atintervals corresponding to the periods of translation of said extraneousmodulations, and means for lproducing a predetermined rate ofattenuation and restoration.

2. In a sound system, the combination of a sound record film havingextraneous light density variations thereon, means for translating saidrecord into electrical currents, a circuit for transmitting saidcurrents, means in said circuit for varying the attenuation of saidcurrents at the intervals of translation of said extraneous lightdensity variations, and means for controlling the rate of attenuation ofsaid circuit during said intervals, said attenuation varying meansincluding a vacuum tube and said controlling means including a source ofpotential for and connected to the elements of said tube and a condenserand resistance connected intermediate said tube elements and said sourceof potential.

3. In a sound system, the combination of a sound reproducer, a soundrecord adapted to be 3 advanced through said sound reproducer, saidsound record having splices therein, a loudspeaker, an electricalcircuit interconnecting said sound reproducer and loudspeaker, and avariable shunt impedance comprising a vacuum tube connected in saidcircuit, variations in the impedance of said vacuum tube being undercontrol of said sound record in said reproducer, and meansinterconnecting said tube and said reproducer for controlling the timeintervals of said impedance variations in said tube and the rate of saidimpedance variations.

t 4. A sound system in accordance with claim 3 1n which said timeinterval control means includes an electrical contactor in said soundreproducer, and said rate control means includes an electrical timingcircuit in the input circuit of said vacuum tube.

5. In a sound system, sound record film, circuit the sound record onsaid cui;i elements comprising gri anode and cathode, means for su l intential to the anode of said tube, msnys ugnxdgr control of said soundrecord for eliminating said potential on said anode, and means connectedintermediate the potential supply for said anode and said anode forpredetermining the rate of decay of said anode potential and the rate'ofrestoration thereof.

6. A sound system in accordance with claim 5 in which saidlast-mentioned means comprises a film-controlled switch for eliminatingthe anode potential and a condenser-resistance timing circuit connectedintermediate said anode and cathode and said anode potential fordetermining the rate of decay of said anode potential and the rate ofrestoration thereof.

7. A sound blooping system comprising a sound record having extraneousdensities therein, means for translating said record into electricalcurrents corresponding mitting said currents, means for attenuating thetransmission of said currents at intervals correthe combination of ameans for reproducing film, one of said cira vacuum tube having spondingto the periods of translation of\ said extraneous densities, and meansfor producing a predetermined rate of attenuation and restora ion.

8. A sound blooping system in accordance with claim .7 in which saidattenuating means comprises an electronic shunt across said currenttransmission means and an cuit for predetermining the variations inimpedance of said electronic shunt.

9. A` circuit for controlling the transmission thereover comprising anampliner, a potential source connected to said amplifier, a switchconnected in the potential supply to said amplifier, and acondenser-resistance network connected intermediate said potentialsource and said amplifier for removing and connecting said poten-` tialsource to said amplifier at an inaudible rate.

10. A circuit in accordance with claim 9 in which said switch issignal-controlled to prevent extraneous signals from being transmittedover said circuit.

BARTON KREUZER.

thereto, means for trans-' electrical timing cir-

